September 29, 2006
Here we go this weekend with a big cooldown. I’m pretty confident it’ll feel like October by the time we get to Monday morning.
High pressure beginning to weaken now after sitting over us for a week. A weak cold front will drag through the region during the day Sunday. No model has rain with this system and the onshore flow doesn’t look too strong either, so sunbreaks are likely Sunday afternoon. Some disagreement on the forecast Tuesday-Thursday. I’m assuming the approaching trough of low pressure will move well south and avoid us, giving no chance for rain. If I’m wrong showers will show up Tuesday afternoon or Wednesday. The 80’s are definitely gone for now too.
As for the chart above? I’m still working on graphics for the winter weather meeting. This one shows the peak wind gust each winter at PDX. Interesting that southerly wind has been quite weak the last few winters. I still think we are way overdue for a good 60+ mph southerly blow this winter, although I’ve been saying that for about 3 years and it still hasn’t happened…Mark
September 28, 2006
Still an incredibly stable pattern for tomorrow, then changes coming for the weekend.
The BIG picture shows a longwave ridge sitting overhead that weakens into Saturday, allowing 1 cold front to slip through Sunday morning. Then a new ridge develops next week just to our north & west, while the next shortwave trough slips south and forms a cutoff low over California. Sound familiar? Whether it has anything to do with our developing El Nino, it IS a similar evolution of events that we would expect in an El Nino Winter. It’s a perfect pattern for dry weather over us when a low goes that far south. Northerly or northeast surface flow is the result as we head towards the cool season in this setup. This time of year it should bring the sunshine right back overhead again starting Monday.
I’m working on some more graphics tonight, so I’ll put them online as I did with the snow graphics last night so you folks can argue over them…I assume you have all figured out that they are just thumbnails too, just click for the full-size image…Mark
September 27, 2006
I felt like I left the kids out in the cold last night when I hopped on the computer this morning and realized in all the high pressure/sunshine excitement I forgot to blog. I figure that’s alright though since you seem to talk amongst yourselves just fine without me.
A VERY persistent pattern over us. Ridge of high pressure sits overhead through Friday, then gets beaten down by a pretty good shortwave trough that eventually moves through the Northwest Sunday. Tough call on rain for Sunday. Most likely a few sprinkles or a shower here & there.
The ridge may pop back up again after that, so I’ve "sunnied" up the forecast for next Monday-Wednesday. Of course with 850mb temps around +5 to +9 instead of +17 (today), it’s going to be quite a bit cooler as we head into the first week of October.
By the way, I’m working on some graphics tonight for the annual WHAT WILL THE WINTER BE LIKE? meeting that the Oregon Chapter of the American Meteorological Society sponsors each Fall. This year it’s going to be on October 20th, a Friday, 10am-Noon at OMSI’s auditorium. I highly recommend you try to get there because it’s a real-life version of the constant winter discussion that takes place on this blog. 4 or 5 professionals will give their prognostication for the winter. I don’t forecast for the winter, but start the presentation with a look back at the past year (and last winter). The event is free and open to the public.
Tonight I’m working on that depressing snow chart that shows yearly snow at PDX for the last 130 years. Wow…time to move to Spokane or Missoula if you want to see snow apparently.
A couple of notes on the snow charts:
In December 1995 when the NWS installed the ASOS unit, snow observations stopped, then restarted a few years later. Observations are now taken at the Airport AND Portland Forecast Office, about 4 miles ESE on 122nd Ave near Sandy Blvd. I’ve kept track of both over the years, but sometimes measurements were incorrect or incomplete, especially in the late 1990’s. One other note; the NWS includes snow pellets, hail, & ice pellets (sleet) in the totals. So some trace amounts may just be hail, but not snow…Mark
September 25, 2006
I figure now is a good time to post (3:30pm) because…there is no weather to talk about beyond sunny skies and warm temps.
It’s a rare set of weather maps when you can’t find much change in the 48 hour period. Basically a broad thermal trough extends from near the Coast to the Cascades through Wednesday. The only change is a slight increase in the offshore flow tomorrow and more on Wednesday. This should keep us in the mid 80’s with a peak temperature-wise on Wednesday this week. I’m not sure why the NWS keeps lowering forecast highs for midweek. They have 81 for Wednesday, which goes the opposite direction of my forecast. We’ll see… Then a slow cooling trend for Thursday-Friday. I doubt we’ll see 80 degree temps return to the Coast by the way since the thermal trough never moves back that far west.
As for the weekend, it appears that the ridge weakens and backs offshore slightly once again. ECMWF doesn’t seem to give us rain, but GFS (12z & 18z) does. I’m keeping the forecast partly cloudy with back to normal temps on Sunday-Monday. Of course if later runs of GFS continue to show showers I’ll throw them into the forecast.
Okay, now for the rules on this Blog…it’s gone very well for the last 10 months since we started posting. It’s rare that a TV station can have open discussion with no problems on a website. That’s a credit to you who participate and keep discussion civil. In fact I can only think of maybe 3-4 times in those 10 months where I had to ban a poster. This weekend was one of those times. So what get’s you banned?
1. Copying other posters or impersonating other posters (using their name). It wastes my time tracking down who is doing it, so I have no tolerance for it.
2. Threats of violence, mention of drug use etc…
3. Rude/obnoxious language, even if it isn’t profane.
4. Talking/posting bad words about someone here at KPTV (send me a nasty note instead of posting one for everyone to see!)
How do we ban you? It’s very easy for me to check the IP address (the place the message was sent from). Even if the name/email is the same, the IP will be different. We just block any message sent from that address. This takes care of the problem everytime. Send me a message at firstname.lastname@example.org if you have a problem with this or you think someone was wrongly banned…Mark
September 22, 2006
Wow…quite a stable weather pattern on the way for the next 7 days at least! Upper level ridge is building overhead with 500mb heights above 580dm. Pretty good for late September. Light onshore flow right now turns offshore by Saturday morning. I expect maybe 2-3 millibars of easterly gradient PDX-DLS tomorrow, then an increase to 5-6 mb. Sunday morning. So Sunday should be the gusty east wind day across the metro area, although we’ll see some tomorrow. Not quite as strong as what we saw early in the month, but probably gusts 25-30 metro area and 40-45 at the west end of the Gorge midday Sunday. This time the flow extends all the way offshore, so the beaches reach the 75-85 range too. Perfect weekend out there.
Offshore flow weakends Monday-Tuesday as a strong shortwave dives into the middle of the USA, but then high pressure behind that gives us renewed east wind by Wednesday again. So it’ll be tough to stay below 80 for daytime highs through the end of next week. Very nice after 9 days of pretty gloomy skies.
September 21, 2006
I’m pretty excited about the upcoming weather pattern. A big ridge of high pressure is developing over the Eastern Pacific this evening. It strengthens and moves over the West Coast the next 48 hours. Long range GFS, ECMWF, & Canadian models all show the ridge persisting over or west of us all through next week. Easterly flow develops by Saturday morning and continues through Sunday. This should easily pop our afternoon temperatures up about 20 degrees. Record high temperatures at PDX are in the 90s until midweek, and still over 88 after that, so I don’t think we’ll be breaking any records. Another reason we won’t get REALLY warm is that the ridge is never really forecast to be directly overhead or just to our east. That would give us warmer air aloft. There is also no sign of a marine airmass anytime in the next 7 days, which leaves us with no morning clouds & sunny skies.
Although it’s obviously a very boring pattern for forecasters and fellow weather enthusiasts, it’s great for getting end-of-season activities done (like painting the eaves of my house). Also, easterly wind should make to the Coast at least 1 and maybe both days this weekend. If so, 75-85 is a good possibility…Mark
September 20, 2006
Nice little cold front approaching quickly from the NW tonight. Looks like it’s through the metro area by news time. It should make for a gripping LIVE RADAR presentation (how can you even consider turning the channel?).
Visible satellite shows a sharp clearing line behind the front and several models I’ve looked at cut the precip off quickly behind. Our RPM model here at the station shows only brief orographic (near mountains) rain showers tomorrow morning. So tomorrow will be mostly dry.
Then ridging sets up for Friday through sometime next week. The ridge is centered slightly offshore, which keeps us from getting a real strong Fall east wind event, but there is some easterly flow Sunday-Monday anyway. So I bumped temps up into the lower 80’s for then. ECMWF & GFS show a small shortwave moving by to the north on Tuesday, which may cool us off before the ridge bounces back. The big picture looks like this: 12 days of warm/sunny weather to start September, then we went into a cool/showery pattern for about 9 days. Now we go back into warm/dry for the last 3rd of the month. Seems pretty normal to me!…Mark